Basic scientific disciplines such as chemistry, biology, physics, and materials engineering are evolving and merging into interdisciplinary efforts in applied materials research, nanosciences, and molecular biotechnology. The aim of efforts is to develop advanced nanoparticles for use in a variety of emerging technical and biomedical fields. Recently, metallic, semiconducting, and magnetic nanoparticles have been developed through these efforts that are tailored to applications in electronics, optics, biotechnology, pharmaceutical and biomedical applications as well as for continued investigation in materials research and nanosciences.
The development of nanoparticles is typically conducted using bottom-up molecular design and fabrication methods (e.g., chemical synthesis and molecular self-assembly) rather than top-down methods (e.g., miniaturization). Bottom-up design and fabrication methods focus on creating increasingly larger functional systems from self-assembling molecules and colloidal building blocks. Typically, molecules used in bottom-up design and fabrication methods are selected based on their ability to provide distinct intrinsic functionality, such as steric, optical, electronic, catalytic properties, etc. The molecules should also have predictable tendencies in their specific constitution, configuration, and dynamic properties to ensure specific self-recognition and self-assembly.
For example, large quantities of inorganic nanoparticles can be prepared from various materials by relatively simple methods. The dimension and size distribution of these particles is optimally controlled within fairly narrow ranges. The most common materials used for producing nanoparticles include metals (e.g., Au), metal oxides, semiconductor materials (e.g., Ag2S, CdS, CdSe, and TiO2), and certain polymeric materials. The properties of metallic nanoparticle arrays depends on the size and shape of the colloidal particles they are made from as well as on their spatial arrangement.
Recently, improved understanding of the chemical and physical properties of nanoparticles has allowed researchers to fabricate nanoparticles with specific biocharacteristics and biofunctional groups. Researchers have used advanced recombinant biotechnology techniques to design and fabricate biofunctional groups such as, nucleic acids, proteins, carbohydrate ligands, and supramolecular complexes from the these components, suitable for attachment to organic and inorganic nano-, micro-, and mesosopic scale particles. The attachment of biomacromolecular assemblies to nanoparticles provides a strong potential for the development of novel inorganic materials useful for biosensing, electronics, information processing, and catalytic applications.
Despite advances in nanoparticle design and fabrication, the emerging nanoparticles field still has many problems to overcome. For example, various problems exist in the fabrication of inorganic nanoparticles, including, degradation and inactivation of sensitive biological compounds due to harsh reaction conditions, and unpredictable ligand-exchange reactions that occur at colloid surfaces that hinder the formation of stable bioconjugates. Additionally, the synthesis of stoichiometrically defined nanoparticle-biomolecule complexes is very challenging. Thus, there remains a need for sensitive and low cost biofunctionalized nanoparticle based biosensors for a number of medically important analytes such as cell surface (e.g., bacteria adhesions) ligands.